Plug hole of a rotary piston engine

ABSTRACT

A plug hole of a rotary piston engine, said hole including a plug mounting hole and an ignition hole which communicates with said plug hole and opens to a trochoidal inner peripheral surface of a center housing of the engine at a position located behind the short axis of trochoid as seen in the rotational direction of the rotor, wherein said ignition hole is formed with a notch at a front portion thereof as seen in the rotational direction of the rotor.

United States Patent Sasaki et al. 1 1 Aug. 5, 1975 [54] PLUG HOLE OF A ROTARY PISTON 3.848.574 11/1974 Fujikuwa et a]. 1. 123/809 ENGINE [751 Inventors: Yoshio Sasaki; Tsuyoshi Yam-azaki. prinuuiv w 1 L. Freeh both of y h Japan Assislan! Evt'unu'm'r-Michuel KOCZO, Jr. [73} Assignee: Toyota Jidosha Kmlyo Kabushiki Alrurney Agent. or FzrnzStewart and Kolasch Ltd.

Kaisha, Toyota, Japan 22 F] d: Ma 31, I974 I e y 5 71 ABSTRACT [21] Appl. No: 475.l82

A plug hole of a rotary piston engine. said hole includl30| Foreign Application Prioriy Data mg a plug mounting hole and an ignition hole whlch 4 974 J 49 430% communicates with said plug hole and opens to a tro- Md) l choidal inner peripheral surface of a center housing of 1521 ms. Cl. 12313.09 the 5 "f mate of trochold is seen in the rotational direction of the [51] lnLCl. .vF02b53/l2 h hl f d 58] Field of Search 1 7/8 01 8119 s 45 W mm o e 'T a notch at a front portion thereof as seen in the rota- 156' References cued tionai dlrectlon of the rotor.

UNITED STATES PATENTS 5 Claims, 5 Drawing Figures 3.777.720 12/1973 Williams 123/2409 PATENTEUMIB 191s SHEET Fl 6. I

Va i FIG.3

glz l3 PLUG HOLE OF A ROTARY PISTON ENGINE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to a rotary piston engine and, more particularly, a plug hole of a rotary piston engine, said engine being of the type comprising a casing composed of a center housing having a trochoidal inner peripheral surface and side housings closing opposite sides of said center housing and a polygonal rotor adapted to rotate eccentrically in said casing with its apex seals provided at its apex portions contacting said inner peripheral surface of said center housing, said plug hole comprising a plug mounting hole and an ignition hole which communicates with said plug mounting hole and opens to said inner peripheral surface of said center housing at a position located behind the short axis of trochoid as seen in the rotational direction of the rotor.

2. Description of the Prior Art In the rotary piston engine of the aforementioned type wherein the ignition hole opens to the inner peripheral surface of the center housing at a position located behind the short axis of trochoid as seen in the rotational direction of the rotor, when one of said apex seals traverses said ignition hole, the combustion chamher which precedes said one apex seal as seen in the rotational direction of the rotor is performing a combustion stroke while another combustion chamber which succeeds said one apex seal is performing a compression stroke, whereby the pressure in the preceding combustion chamber is substantially higher than that in the succeeding combustion chamber or, in other words, there exists a relatively large pressure difference between the two combustion chambers. Because of this large pressure difference, it has not conventionally been allowed to provide a large ignition hole. When the ignition hole is relatively small, scavenging thereof is not sufficiently effected, ignition becomes unstable, and particularly when the engine has been started up in a cold condition, droplets of fuel, carbon sludge, droplets of water formed by the cooling down of steam generated by combustion of fuel, etc., are apt to fill the ignition hole, whereby the starting up of the engine is made difficult.

As a measure to counteract these problems, it has been proposed to provide a passage which connects with the plug mounting hole at one end thereof and opens to the inner peripheral surface of the center housing at the other end thereof at a position located behind the open end of the ignition hole as seen in the rotational direction of the rotor so that when one of the apex seals has come between the open end of said passage and that of the ignition hole, combustible gases residing in a trailing portion of a combustion chamber which precedes said one apex seal and is performing a combustion stroke is blown to a combustion chamber which succeeds said one apex seal and is performing a compression stroke through the ignition hole and said passage (Japanese Utility Model Publication 22276/71). In this constitution, however, a cylindrical housing forming the tip portion of an ignition plug must be formed with an annular groove along its outer peripheral portion and a number of radial openings which open to said annular groove so as to establish a flow passage which connects the ignition hole to said passage and, accordingly, this system is bound with a drawback that the structure of the tip portion of the spark plug becomes rather complicated.

SUMMARY OF THE INVENTION Therefore, it is the object of this invention to provide a simple structure of a plug hole which does not require any special working of the tip portion of the spark plug as required in the case of said Japanese Utility Model Publication, yet can accomplish sufficient scavenging of the ignition hole.

According to this invention, the abovementioned object is accomplished by a plug hole of the constitution as described in the opening paragraph of this specification, characterized in that said ignition hole is formed with a notch at a front portion thereof as seen in the rotational direction of the rotor, said notch operating to lead combustible gases residing in a trailing portion of a preceding combustion chamber performing a combustion stroke into said plug mounting hole when one of said apex seals traverses said ignition hole.

According to a particular feature of this invention, said notch should preferably be narrower than the diameter of said ignition hole and stretched as inclined with respect to the axis of said ignition hole.

Said notch may be provided in substantially the same manner in either case where said ignition hole is substantially aligned with said plug mounting hole along the same axis, said ignition hole is displaced forward as seen in the rotational direction of the rotor with respect to said plug mounting hole, or said ignition hole is displaced rearward as seen in the rotational direction of the rotor with respect to said plug mounting hole. In either case regarding the arrangement of said ignition hole and plug mounting hole, combustible gases residing in a trailing portion of the preceding combustion chamber performing a combustion stroke is introduced into the plug mounting hole through said notch when an apex seal traverses the ignition hole, whereby good scavenging of a passage extending from the plug mounting hole to the ignition hole is accomplished.

BRIEF DESCRIPTION OF THE DRAWING In the accompanying drawing,

FIG. 1 is a sectional view showing a basic structure of a rotary piston engine, wherein, however, the rotor is shown in its side view to show its side structure;

FIG. 2 is a sectional view of a plug hole portion showing the structure of the plug hole according to this invention, wherein, however, the rotor is shown in its side view to show its side structure;

FIG. 3 is a view of an inner peripheraal surface of the center housing taken in the direction of arrows DD in FIG. 2, showing the cross sectional structure of the ignition hole and said notch; and,

FIGS. 4 and 5 are views similar to FIG. 2, showing modifications of the plug hole structure according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the following, this invention will be described in more detail of some preferred embodiments with reference to the accompanying drawing.

FIG. 1 shows a general structure of a rotary piston engine which comprises a center housing I having a trochoidal inner peripheral surface and side housings 2 closing opposite ends of said center housings thereby to form a casing in which a polygonal rotor 3 rotates eccentrically about an eccentric shaft 5 with its apex seals 4 provided at its apex portions contacting said inner peripheral surface of said center housing. The rotary piston engine of this type may be constituted in two different structures wherein either a spark plug 6 is positioned behind the short axis of trochoid CC as seen in the rotational direction of the rotor or a spark plug 6' is positioned before said axis as seen in the rotational direction of the rotor. As already mentioned, this invention relates to the plug hole structure which employs the plug 6 positioned behind said short axis of trochoid CC as seen in the rotational direction of the rotor. In FIG. 1, reference numerals 7 and 8 designate annular oil seal means to keep oil and gas tightness between a side wall of the rotor and an inner wall of the side housing. 9 is a side seal to keep oil and gas tightness at peripheral edge portions of the rotor, and 10 is a corner seal.

FIG. 2 shows a basic embodiment of the plug hole structure according to this invention. In FIG. 2, the portions corresponding to those shown in FIG. 1 are designated by the same reference numerals as in FIG. 1. The tip portion of the spark plug 6 is mounted in a plug mounting hole II formed in the center housing 1, said plug mounting hole communicating to the combus tion chamber of the engine defined between the center housing I and the rotor 3 by way of an ignition hole 12 which connects with said plug mounting hole at one end thereof and opens to the inner peripheral surface of the center housing 1 at a position located behind the short axis of the trochoid CC as seen in the rotational direction of the rotor. The ignition hole I2 is formed with a notch I3 at a front portion thereof as seen in the rotational direction of the rotor according to this invention. The notch I3 is, as better shown in FIG. 3 which shows the opening shape thereof, narrower than the diameter of the ignition hole 12, and stretched, as shown in FIG. 2, as inclined with respect to the axis of the ignition hole I2.

When one of the apex seals 4 has come to the position as shown in FIG. 1, a combustion chamber A located behind said one apex seal as seen in the rotational direction of the rotor is performing a compression stroke, while a combustion chamber B located before said one apex seal as seen in the rotational direction of the rotor is performing a combustion stroke. Therefore, by providing the notch 13 of the aforementioned kind, a part of combustion gases which is rich in combustible gases and resides in a trailing portion of the combustion chamber B performing a combustion stroke is introduced into the plug mounting hole II through said notch I3 and further flows into the combustion chamber A through the ignition hole 12 while scavenging the plug mounting hole and the ignition hole due to a pressure difference between the combustion chambers B and A, the pressure in the former chamber being substantially higher than that in the latter chamber.

FIG. 4 is a view similar to FIG. 2, showing a modification of the plug hole incorporating the notch according to this invention. In FIG. 4, the portions corresponding to those shown in FIG. 2 are designated by the same reference numerals as in FIG. 2. In the structure shown in FIG. 4, the ignition hole 12 is displaced forward with respect to the plug mounting hole II as seen in the rotational direction of the rotor so far that the front faces, as seen in the rotational direction of the rotor, of the plug mounting hole and the ignition hole are aligned with each other. In this arrangement of the plug mounting hole and the ignition hole, it has been confirmed that a substantially same scavenging of the plug mounting hole as in the case of the structure shown in FIG. 2 is obtained by providing the notch I3.

FIG. 5 is a view similar to FIG. 2 or 4, showing another modification of the plug hole structure according to this invention, wherein the ignition hole is displaced rearward as seen in the rotational direction of the rotor with respect to the plug mounting hole. In FIG. 5, the portions corresponding to those shown in FIG. 2 or 4 are designated by the same reference numerals as in FIg. 2 or 4. It has also been confirmed that, in the arrangement of the plug mounting hole II and the ignition hole 12 as shown in FIG. 5, substantially same scavenging of the plug mounting hole as in the case of the structure shown in FIG. 2 or 4 is attained.

From the foregoing, it will be appreciated that the structure of the plug hole incorporating the notch according to this invention is very simple, yet effective scavenging of the plug mounting hole is accomplished by utilizing the pressure difference residing between two combustion chambers defined at opposite sides of an apex seal.

We claim:

1. A plug hole of a rotary piston engine, said engine being of the type comprising a casing composed of a center housing having a trochoidal inner peripheral surface and side housings closing opposite sides of said center housing and a polygonal rotor adapted to rotate eccentrically in said casing with its apex seals provided at its apex portions contacting said inner peripheral surface of said center housing, said plug hole comprising a plug mounting hole and an ignition hole which communicates with said plug mounting hole and opens to said inner peripheral surface of said center housing at a position located behind the short axis of trochoid as seen in the rotational direction of the rotor, characterized in that said ignition hole is formed with a notch at a front portion thereof as seen in the rotational direction of the rotor, said notch operating to lead com bustibIe gases residing in a trailing portion of a preceding combustion chamber performing a combustion stroke into said plug mounting hole when one of said apex seals traverses said ignition hole.

2. A plug hole according to claim 1, wherein said notch is narrower than the diameter of said ignition hole and stretched as inclined with respect to the axis of said ignition hole.

3. A plug hole according to claim I, wherein said ignition hole is substantially axially aligned with said plug mounting hole.

4. A plug hole according to claim 1, wherein said ignition hole is displaced forward as seen in the rotational direction of the rotor with respect to said plug mounting hole.

5. A plug hole according to claim I, wherein said ignition hole is displaced rearward as seen in the rotational direction of the rotor with respect to said plug mounting hole. 

1. A plug hole of a rotary piston engine, said engine being of the type comprising a casing composed of a center housing having a trochoidal inner peripheral surface and side housings closing opposite sides of said center housing and a polygonal rotor adapted to rotate eccentrically in said casing with its apex seals provided at its apex portions contacting said inner peripheral surface of said center housing, said plug hole comprising a plug mounting hole and an ignition hole which communicates with said plug mounting hole and opens to said inner peripheral surface of said center housing at a position located behind the short axis of trochoid as seen in the rotational direction of the rotor, characterized in that said ignition hole is formed with a notch at a front portion thereof as seen in the rotational direction of the rotor, said notch operating to lead combustible gases residing in a trailing portion of a preceding combustion chamber performing a combustion stroke into said plug mounting hole when one of said apex seals traverses said ignition hole.
 2. A plug hole according to claim 1, wherein said notch is narrower than the diameter of said ignition hole and stretched as inclined with respect to the axis of said ignition hole.
 3. A plug hole according to claim 1, wherein said ignition hole is substantially axially aligned with said plug mounting hole.
 4. A plug hole according to claim 1, wherein said ignition hole is displaced forward as seen in the rotational direction of the rotor with respect to said plug mounting hole.
 5. A plug hole according to claim 1, wherein said ignition hole is displaced rearward as seen in the rotational direction of the rotor with respect to said plug mounting hole. 